bcachefs: Refactor journal code to not use unwritten_idx

It makes the code more readable if we work off of sequence numbers,
instead of direct indexes into the array of journal buffers.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/journal.c

@@ -19,11 +19,6 @@
 #include "super-io.h"
 #include "trace.h"
 
-static u64 last_unwritten_seq(struct journal *j)
-{
-	return j->seq_ondisk + 1;
-}
-
 static inline bool journal_seq_unwritten(struct journal *j, u64 seq)
 {
 	return seq > j->seq_ondisk;
@@ -34,6 +29,11 @@ static bool __journal_entry_is_open(union journal_res_state state)
 	return state.cur_entry_offset < JOURNAL_ENTRY_CLOSED_VAL;
 }
 
+static inline unsigned nr_unwritten_journal_entries(struct journal *j)
+{
+	return atomic64_read(&j->seq) - j->seq_ondisk;
+}
+
 static bool journal_entry_is_open(struct journal *j)
 {
 	return __journal_entry_is_open(j->reservations);
@@ -166,6 +166,7 @@ static bool __journal_entry_close(struct journal *j)
 	 */
 	buf->last_seq		= journal_last_seq(j);
 	buf->data->last_seq	= cpu_to_le64(buf->last_seq);
+	BUG_ON(buf->last_seq > le64_to_cpu(buf->data->seq));
 
 	__bch2_journal_pin_put(j, le64_to_cpu(buf->data->seq));
 
@@ -179,18 +180,19 @@ static bool __journal_entry_close(struct journal *j)
 
 static bool journal_entry_want_write(struct journal *j)
 {
-	union journal_res_state s = READ_ONCE(j->reservations);
-	struct journal_buf *buf = journal_cur_buf(j);
-	bool ret = false;
-
-	if (!buf->flush_time) {
-		buf->flush_time	= local_clock() ?: 1;
-		buf->expires = jiffies;
-	}
+	bool ret = !journal_entry_is_open(j) ||
+		(journal_cur_seq(j) == journal_last_unwritten_seq(j) &&
+		 __journal_entry_close(j));
 
 	/* Don't close it yet if we already have a write in flight: */
-	if (s.idx == s.unwritten_idx)
-		ret = __journal_entry_close(j);
+	if (!ret && nr_unwritten_journal_entries(j)) {
+		struct journal_buf *buf = journal_cur_buf(j);
+
+		if (!buf->flush_time) {
+			buf->flush_time	= local_clock() ?: 1;
+			buf->expires = jiffies;
+		}
+	}
 
 	return ret;
 }
@@ -310,8 +312,8 @@ static int journal_entry_open(struct journal *j)
 
 static bool journal_quiesced(struct journal *j)
 {
-	union journal_res_state s = READ_ONCE(j->reservations);
-	bool ret = s.idx == s.unwritten_idx && !__journal_entry_is_open(s);
+	bool ret = atomic64_read(&j->seq) == j->seq_ondisk ||
+		bch2_journal_error(j);
 
 	if (!ret)
 		journal_entry_close(j);
@@ -416,7 +418,7 @@ static int __journal_res_get(struct journal *j, struct journal_res *res,
 	if ((ret == cur_entry_journal_full ||
 	     ret == cur_entry_journal_pin_full) &&
 	    !can_discard &&
-	    j->reservations.idx == j->reservations.unwritten_idx &&
+	    !nr_unwritten_journal_entries(j) &&
 	    (flags & JOURNAL_RES_GET_RESERVED)) {
 		struct printbuf buf = PRINTBUF;
 
@@ -576,7 +578,7 @@ int bch2_journal_flush_seq_async(struct journal *j, u64 seq,
 	}
 
 	/* if seq was written, but not flushed - flush a newer one instead */
-	seq = max(seq, last_unwritten_seq(j));
+	seq = max(seq, journal_last_unwritten_seq(j));
 
 recheck_need_open:
 	if (seq > journal_cur_seq(j)) {
@@ -709,13 +711,13 @@ bool bch2_journal_noflush_seq(struct journal *j, u64 seq)
 	if (seq <= c->journal.flushed_seq_ondisk)
 		goto out;
 
-	for (unwritten_seq = last_unwritten_seq(j);
+	for (unwritten_seq = journal_last_unwritten_seq(j);
 	     unwritten_seq < seq;
 	     unwritten_seq++) {
 		struct journal_buf *buf = journal_seq_to_buf(j, unwritten_seq);
 
 		/* journal write is already in flight, and was a flush write: */
-		if (unwritten_seq == last_unwritten_seq(j) && !buf->noflush)
+		if (unwritten_seq == journal_last_unwritten_seq(j) && !buf->noflush)
 			goto out;
 
 		buf->noflush = true;
@@ -940,17 +942,16 @@ int bch2_dev_journal_alloc(struct bch_dev *ca)
 
 static bool bch2_journal_writing_to_device(struct journal *j, unsigned dev_idx)
 {
-	union journal_res_state state;
 	bool ret = false;
-	unsigned i;
+	u64 seq;
 
 	spin_lock(&j->lock);
-	state = READ_ONCE(j->reservations);
-	i = state.idx;
+	for (seq = journal_last_unwritten_seq(j);
+	     seq <= journal_cur_seq(j) && !ret;
+	     seq++) {
+		struct journal_buf *buf = journal_seq_to_buf(j, seq);
 
-	while (i != state.unwritten_idx) {
-		i = (i - 1) & JOURNAL_BUF_MASK;
-		if (bch2_bkey_has_device(bkey_i_to_s_c(&j->buf[i].key), dev_idx))
+		if (bch2_bkey_has_device(bkey_i_to_s_c(&buf->key), dev_idx))
 			ret = true;
 	}
 	spin_unlock(&j->lock);
@@ -1012,6 +1013,7 @@ int bch2_fs_journal_start(struct journal *j, u64 cur_seq,
 	j->replay_journal_seq_end = cur_seq;
 	j->last_seq_ondisk	= last_seq;
 	j->flushed_seq_ondisk	= cur_seq - 1;
+	j->seq_ondisk		= cur_seq - 1;
 	j->pin.front		= last_seq;
 	j->pin.back		= cur_seq;
 	atomic64_set(&j->seq, cur_seq - 1);
@@ -1164,15 +1166,18 @@ void __bch2_journal_debug_to_text(struct printbuf *out, struct journal *j)
 	union journal_res_state s;
 	struct bch_dev *ca;
 	unsigned long now = jiffies;
+	u64 seq;
 	unsigned i;
 
 	out->atomic++;
+	out->tabstops[0] = 24;
 
 	rcu_read_lock();
 	s = READ_ONCE(j->reservations);
 
-	pr_buf(out, "active journal entries:\t%llu\n",	fifo_used(&j->pin));
+	pr_buf(out, "dirty journal entries:\t%llu\n",	fifo_used(&j->pin));
 	pr_buf(out, "seq:\t\t\t%llu\n",			journal_cur_seq(j));
+	pr_buf(out, "seq_ondisk:\t\t%llu\n",		j->seq_ondisk);
 	pr_buf(out, "last_seq:\t\t%llu\n",		journal_last_seq(j));
 	pr_buf(out, "last_seq_ondisk:\t%llu\n",		j->last_seq_ondisk);
 	pr_buf(out, "flushed_seq_ondisk:\t%llu\n",	j->flushed_seq_ondisk);
@@ -1191,33 +1196,42 @@ void __bch2_journal_debug_to_text(struct printbuf *out, struct journal *j)
 
 	switch (s.cur_entry_offset) {
 	case JOURNAL_ENTRY_ERROR_VAL:
-		pr_buf(out, "error\n");
+		pr_buf(out, "error");
 		break;
 	case JOURNAL_ENTRY_CLOSED_VAL:
-		pr_buf(out, "closed\n");
+		pr_buf(out, "closed");
 		break;
 	default:
-		pr_buf(out, "%u/%u\n", s.cur_entry_offset, j->cur_entry_u64s);
+		pr_buf(out, "%u/%u", s.cur_entry_offset, j->cur_entry_u64s);
 		break;
 	}
 
-	pr_buf(out, "current entry:\t\tidx %u refcount %u\n", s.idx, journal_state_count(s, s.idx));
+	pr_newline(out);
 
-	i = s.idx;
-	while (i != s.unwritten_idx) {
-		i = (i - 1) & JOURNAL_BUF_MASK;
+	for (seq = journal_cur_seq(j);
+	     seq >= journal_last_unwritten_seq(j);
+	     --seq) {
+		i = seq & JOURNAL_BUF_MASK;
 
-		pr_buf(out, "unwritten entry:\tidx %u refcount %u sectors %u\n",
-		       i, journal_state_count(s, i), j->buf[i].sectors);
+		pr_buf(out, "unwritten entry:");
+		pr_tab(out);
+		pr_buf(out, "%llu", seq);
+		pr_newline(out);
 		pr_indent_push(out, 2);
 
-		pr_buf(out, "refcount %u", journal_state_count(s, i));
+		pr_buf(out, "refcount:");
+		pr_tab(out);
+		pr_buf(out, "%u", journal_state_count(s, i));
 		pr_newline(out);
 
-		pr_buf(out, "sectors %u", j->buf[i].sectors);
+		pr_buf(out, "sectors:");
+		pr_tab(out);
+		pr_buf(out, "%u", j->buf[i].sectors);
 		pr_newline(out);
 
-		pr_buf(out, "expires %li ms", jiffies_to_msecs(j->buf[i].expires - jiffies));
+		pr_buf(out, "expires");
+		pr_tab(out);
+		pr_buf(out, "%li jiffies", j->buf[i].expires - jiffies);
 		pr_newline(out);
 
 		pr_indent_pop(out, 2);

fs/bcachefs/journal.h

@@ -141,6 +141,11 @@ static inline u64 journal_cur_seq(struct journal *j)
 	return j->pin.back - 1;
 }
 
+static inline u64 journal_last_unwritten_seq(struct journal *j)
+{
+	return j->seq_ondisk + 1;
+}
+
 static inline int journal_state_count(union journal_res_state s, int idx)
 {
 	switch (idx) {

fs/bcachefs/journal_io.c

@@ -1331,7 +1331,7 @@ static void journal_buf_realloc(struct journal *j, struct journal_buf *buf)
 
 static inline struct journal_buf *journal_last_unwritten_buf(struct journal *j)
 {
-	return j->buf + j->reservations.unwritten_idx;
+	return j->buf + (journal_last_unwritten_seq(j) & JOURNAL_BUF_MASK);
 }
 
 static void journal_write_done(struct closure *cl)
@@ -1403,12 +1403,13 @@ static void journal_write_done(struct closure *cl)
 	closure_wake_up(&w->wait);
 	journal_wake(j);
 
-	if (new.unwritten_idx == new.idx) {
+	if (journal_last_unwritten_seq(j) == journal_cur_seq(j)) {
 		struct journal_buf *buf = journal_cur_buf(j);
 		long delta = buf->expires - jiffies;
 
 		mod_delayed_work(c->io_complete_wq, &j->write_work, max(0L, delta));
-	} else if (!journal_state_count(new, new.unwritten_idx))
+	} else if (journal_last_unwritten_seq(j) < journal_cur_seq(j) &&
+		   !journal_state_count(new, new.unwritten_idx))
 		closure_call(&j->io, bch2_journal_write, c->io_complete_wq, NULL);
 
 	spin_unlock(&j->lock);

fs/bcachefs/journal_reclaim.c

@@ -59,25 +59,13 @@ static void journal_set_remaining(struct journal *j, unsigned u64s_remaining)
 				       old.v, new.v)) != old.v);
 }
 
-static inline unsigned get_unwritten_sectors(struct journal *j, unsigned *idx)
-{
-	unsigned sectors = 0;
-
-	while (!sectors && *idx != j->reservations.idx) {
-		sectors = j->buf[*idx].sectors;
-
-		*idx = (*idx + 1) & JOURNAL_BUF_MASK;
-	}
-
-	return sectors;
-}
-
 static struct journal_space
 journal_dev_space_available(struct journal *j, struct bch_dev *ca,
 			    enum journal_space_from from)
 {
 	struct journal_device *ja = &ca->journal;
-	unsigned sectors, buckets, unwritten, idx = j->reservations.unwritten_idx;
+	unsigned sectors, buckets, unwritten;
+	u64 seq;
 
 	if (from == journal_space_total)
 		return (struct journal_space) {
@@ -92,7 +80,14 @@ journal_dev_space_available(struct journal *j, struct bch_dev *ca,
 	 * We that we don't allocate the space for a journal entry
 	 * until we write it out - thus, account for it here:
 	 */
-	while ((unwritten = get_unwritten_sectors(j, &idx))) {
+	for (seq = journal_last_unwritten_seq(j);
+	     seq <= journal_cur_seq(j);
+	     seq++) {
+		unwritten = j->buf[seq & JOURNAL_BUF_MASK].sectors;
+
+		if (!unwritten)
+			continue;
+
 		/* entry won't fit on this device, skip: */
 		if (unwritten > ca->mi.bucket_size)
 			continue;
@@ -214,8 +209,7 @@ void bch2_journal_space_available(struct journal *j)
 	total		= j->space[journal_space_total].total;
 
 	if (!clean_ondisk &&
-	    j->reservations.idx ==
-	    j->reservations.unwritten_idx) {
+	    journal_cur_seq(j) == j->seq_ondisk) {
 		struct printbuf buf = PRINTBUF;
 
 		__bch2_journal_debug_to_text(&buf, j);

fs/bcachefs/journal_types.h

@@ -25,7 +25,7 @@ struct journal_buf {
 
 	struct closure_waitlist	wait;
 	u64			last_seq;	/* copy of data->last_seq */
-	unsigned long		expires;
+	long			expires;
 	u64			flush_time;
 
 	unsigned		buf_size;	/* size in bytes of @data */